Electric ion with safety system controlling electric heater depending on total supply time

ABSTRACT

An iron comprises a sole plate heated by an electrical resistance and a heat-regulating system, wherein a control member indicates the temperature set value, a sensor displays the sole plate temperature, and a management system controls the electrical resistance power supply circuit to be opened or closed, on the basis of the difference between the set value and the measurement. The iron comprises a safety system comprising an electronic module, which: a) receives from the management system information for closing the electrical resistance power supply circuit; b) produces over a fixed time interval the total supply times; and c) opens the electrical resistance power supply circuit if the resulting value is less than a predetermined threshold value.

CROSS REFERENCE TO RELATED APPLICATION

This is the 35 USC 371 national stage of International ApplicationPCT/FR99/01117 filed on May 11, 1999, which designated the United Statesof America.

FIELD OF THE INVENTION

The present invention relates to electric irons which comprise a soleplate heated by means of an electric heating resistance and a system ofthermal regulation, in which a control member indicates the referencevalue of the temperature corresponding to the fabric to be ironed, adetector gives the image of the temperature of the sole plate, and acontrol system controls the opening or the closing, as a function of thedifference between the reference temperature and the measuredtemperature, of the supply circuit of the electric heating resistance.

BACKGROUND OF THE INVENTION

In certain known electric irons of this type, there is provided a safetysystem detecting the position of the iron, on the heel or on the soleplate, and cutting the supply of the heating resistance when the iron isleft in a vertical position on the heel during a period greater than acertain limit.

Such a system is adapted to avoid accidental burning of the user or hissurroundings, when the iron is unused and left on. It also permitsavoiding the apparatus being subjected to prolonged and useless heatingcycles, when the latter is accidentally left on.

Such a system nevertheless has the drawback of using a physical positiondetector, which increases the cost of the apparatus, increases its sizeand has decreased reliability with time and the cycles of use.

SUMMARY OF THE INVENTION

The invention proposes overcoming these drawbacks and providing an ironof the type described above, provided with a safety system without aposition detector, capable of detecting reliably the stoppage of use ofthe apparatus.

According to the invention, the iron comprises a safety system having anelectronic module which:

a) receives from the control system the information as to closure of thesupply circuit of the electric heating resistance,

b) produces over a fixed time interval the sum of the durations ofsupply,

c) and opens the supply circuit of the electric heating resistance ifthe value thus obtained is below a predetermined threshold value.

Thus the system detects a magnitude represented by the quantity of heatdelivered by the apparatus, characteristic of contact of the sole with acloth or with ambient air.

According to an advantageous characteristic of the invention, theelectronic module comprises a switch mounted in series with the electricheating resistance, which is actuated in response to a signal deliveredby a first counter.

On the other hand, the first counter comprises a programmable integratedcircuit, which has at least one supply path, a reception path for a zeroset signal, an outlet path, a means for the generation of an activatedclock frequency upon turning on the iron.

Moreover, the first counter delivers an opening signal to a relay whosecontacts form the switch, when it has carried out an operation ofcounting of a time lag greater than predetermined time T1, withoutreceiving the zero set signal, T1 being greater than T2.

Preferably, the first counter delivers simultaneously an opening signalto a relay whose contacts form the switch and a lockage signal for themeans for generating associated clock frequency to the first counter,after it has carried out a counting operation of a duration greater thana predetermined time T1, without receiving a zero set signal, T1 beinggreater than T2.

According to another characteristic of the invention, the safety systemcomprises rearming means that can be actuated by the user, so as toclose the relay and reactivate the means for generating clock frequencyassociated with the first counter, when the iron is on.

The rearming means, when actuated by the user, emit a zero set signalsimultaneously to the first and second counter.

According to another embodiment, the safety system comprises anelectronic module which:

a) receives from the control system information as to the closure of thesupply circuit of the electric heating resistance,

b) counts over a fixed time interval the number of alternations betweenopen and closed conditions of the supply circuit of the electric heatingresistance, and opens the supply circuit of the electric heatingresistance if the number thus obtained is below a predeterminedthreshold value.

This other embodiment permits, again by observation of the operation ofthe heating resistance, determining whether the latter is frequentlyurged to compensate the heat losses of the sole plate, and to cut thesupply in the contrary case, which is taken to be characteristic of anonuse condition.

BRIEF DESCRIPTION OF THE DRAWINGS

The different characteristics as well as the advantages of the inventionwill become further apparent from the description which follows, givenby way of non-limiting example, with reference to the accompanyingdrawings, in which:

FIG. 1 is an operational diagram of a safety system according to theinvention;

FIG. 2 is an operational diagram of a safety system according to apreferred embodiment of the invention;

FIG. 3A is a graph connecting the electrical condition of the resistanceand time, in a case of use; and

FIG. 3B is a graph connecting the electrical condition of the resistanceand time in a case of non-use of an iron.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, there is shown the supply circuit 1 of the electric heatingresistance (2) adapted to heat the sole plate of an iron, the electricpower being supplied by the household supply (3). The iron is either adry iron or a steam iron.

The temperature of the sole plate is regulated by means of a controlmember (4), generally actuated by the user, which fixes the referencetemperature, by a temperature detector (5) located adjacent the soleplate and which gives the image of the temperature of the sole plate,and a control system (6), which actuates a first switch (7) disposed inthe supply circuit (1) of the electric heating resistance (2), as afunction of the difference between the temperature of the sole plate andthe reference temperature, such that the temperature of the sole platewill be constantly located in a predetermined range about the referencetemperature.

At present, this system of regulation is simply constituted by amechanical thermostat or, in apparatus of a wider range, comprises apotentiometer and electronic regulation means.

The supply circuit (1) of the electric heating resistance (2) comprises,according to the invention, a second switch (8) actuated by anelectronic module (9) when the safety system (10) detects a non-usecondition of the apparatus beyond a certain limit.

The safety system (10) receives a signal (11) from the control system(6), representative of the condition of the first switch (7), and henceof the supplied or non-supplied condition of the electric heatingresistance (2), the second switch (8) being closed under the initialcondition of the safety system (10), at the moment of connection of theapparatus to the sector.

In FIG. 2, there is shown a safety system according to a preferredembodiment of the invention, in which the safety system (10) is suppliedwith alternating current by the domestic network (3), by means of aso-called “positive” route (P) and a so-called “neutral” route (N), saidsafety system (10) also retaining the potential at one of the terminalsof the heating resistance (2) by means of a third path (X), such as saidheating resistance (2) namely located between the “neutral” path (N) andthe third path (X).

The safety system (10) comprises a first connector (12) with two pathspermitting connecting the switch (8) with the heating resistance (2),the two inlet paths being the positive path (P) and the third path (X).The safety system (1) comprises a second connector (13) with two paths,which receives the reference potential by the neutral path (N) and thecondition information as to the heating resistance (2) by the third path(X).

The electronic module (9) comprises two modules (14, 15) processing theelectric signals passing through the three paths (N, P, X) so as toobtain continuous signals of an intensity permissible to the components,namely respectively a reference potential (V_(ss)), a potential (V_(cc))defining with it a supply voltage for the active components of theelectronic module (9), and a potential for condition information (x) ofthe heating resistance (2).

The electronic module (9) comprises a first and second counter (21, 22)each comprising a programmable integrated circuit, which has at leastone supply path (A1, A2) set to the potential (V_(cc)) when theapparatus is on, a reception path for a zero set signal (R1, R2), and anoutput path (S1, S2), and means for generating clock frequency suppliedby a supply path of the means for generating the clock frequency (H1, H2).

The electronic module (9) moreover comprises a first bipolar transistor(16), whose base is connected to the output path (S1) of the firstprogrammable integrated circuit (21) by means of a resistance (18), theemitter is connected to the supply path of the means for generatingclock frequency (H1) of the first counter (21), and the collector to theline of reference potential (V_(ss)); a second bipolar transistor (17)whose base receives the signal corresponding to the conditioninformation potential (x) of the heating resistance, the emitter isconnected to the supply path of the clock frequency generation means(H2) of the second programmable integrated circuit (22), and thecollector to the line of reference potential (V_(ss)).

The signal delivered by the first counter (21) on its output path (S1)is transmitted to a relay (20), which causes opening of closing of thesupply circuit of the heating resistance, via the switch (8) formed byits contacts.

Upon turning on the iron, the means for generating clock frequency ofthe first counter (21) are supplied and the heating resistance beingsupplied, the means for generating clock frequency of the second counter(22) are also supplied. The second counter (22) is incremented while theheating resistance (2) is supplied, and carries out the addition of thesupply times of said resistance. The second counter (22) emits an end ofcycle signal on its outlet path (S2), via a resistance (19), as soon asit has carried out a counting operation of a duration greater than apredetermined time T2. This end of cycle signal is directed toward thezero set path (R2) of the second counter (22) and in parallel to thezero set path (R1) of the first counter (21).

If the first counter (21) has carried out a counting operation of aduration greater than a predetermined time T1, without having received azero set signal on its reception path (R1), it emits on its outlet path(S1) a signal to the relay (20), which opens the supply circuit of theheating resistance, this cutoff signal also effecting, via the firsttransistor (16), the blocking of the clock frequency generating means ofthe first counter.

Rearmament means (23) are provided to permit the user to turn on theiron again and to restart the safety system, when the latter has cut offthe supply of the heating resistance following the detection of aprolonged non-use condition.

These re-arming means (23), when they are actuated by the user, emit animpulse on the zero set paths (R1, R2) of the first and second counters(21, 22), which has the effect of re-establishing the outlet path (S1)of the first counter (21) in its initial condition, and thus unblockingits clock frequency generating means and causing, by a new openingsignal of the relay (20), the closure of the switch (8) and hence of thesupply circuit of the heating resistance (2).

As a result of the system described above, the safety system accordingto the invention cuts the supply circuit of the heating resistance (2),reversibly thanks to the rearmament means (23) if in the course of atime interval T1, for example of the order of six minutes, the heatingtime of the heating resistance has not reached a limit T2, for exampleof the order of 25 seconds, which condition characterizes a non-usecondition of the apparatus.

Thus, as can be seen in FIGS. 3A and 3B, it is possible to characterizea use condition corresponding to the graph 3 a, relative to a non-usecondition corresponding to the graph 3 b, either by a larger totalsupply time, or by a higher frequency of the supply phases.

Thanks to this safety system, whether applied to a dry iron or a steamiron, there is obtained a reading of the image of the temperature of thesole plate which reflects either a thermal exchange with a cloth to bepressed to deduce the operating position of the sole plate, or a thermalexchange with the air to deduce the vertical position of the sole plate.

What is claimed is:
 1. Electric iron comprising a sole plate heated bymeans of a heating electric resistance (2) and a system of thermalregulation, in which a control member (4) indicates the reference valueof temperature corresponding to the cloth to be pressed, a detector (5)gives the temperature of the sole plate, and a control system (6)controls the opening or closing of the supply circuit (1) of theelectric heating resistance (2), as a function of the difference betweenthe reference temperature and the measured temperature, wherein the ironfurther comprises a safety system (10) comprising an electronic module(9), which: a) receives from the control system (6) information as tothe closure of the supply circuit (1) of the electric heating resistance(2), b) carries out over a fixed time interval the summation of thesupply times, and c) opens the supply circuit (1) of the electricheating resistance (2) if the value thus obtained is below apredetermined threshold value.
 2. The electric iron according to claim1, wherein the electronic module (9) comprises a switch (8) mounted inseries with the electric heating resistance (2), which is actuated inresponse to a signal from a first counter (21).
 3. The electric ironaccording to claim 2, wherein the first counter (21) comprises aprogrammable integrated circuit, which has at least one supply path(A1), a reception path (R1) for a signal set zero, an outlet path (S1),and means for generating clock frequency (H1) activated upon turning onthe iron.
 4. The electric iron according to claim 3, wherein theelectronic module (9) comprises a second counter (22), which comprises aprogrammable integrated circuit, having at least one supply path (A2), apath for reception of a zero set signal (R2), an outlet path (S2), andmeans for generating clock frequency (H2) actuated when the electricheating resistance (2) is supplied.
 5. The electric iron according toclaim 4, wherein the second counter (22) addresses to the first andsecond counters (21, 22) a zero set signal, since said second counter(22) has carried out a counting operation of a duration greater than apredetermined time T2 without receiving a zero set signal.
 6. Theelectric iron according to claim 5, wherein the first counter (21)delivers an opening signal to a relay (20) whose contacts form theswitch (8), since it has carried out a counting operation of a durationgreater than a predetermined time T1, without receiving a zero setsignal, T1 being greater than T2.
 7. The electric iron according toclaim 6, wherein the safety system (10) comprises rearmament means (23)that can be actuated by the user so as to close the relay (20) and toreactivate the means for generating clock frequency (H1) associated withthe first counter 21, when the iron is on.
 8. The electric ironaccording to claim 7, wherein the rearmament means (23), when actuatedby the user, emit a zero set signal simultaneously toward the first andsecond counters (21, 22).
 9. The electric iron according to claim 5,wherein the first counter (21) simultaneously delivers an opening signalto a relay (20) whose contacts form the switch (8) and a blocking signalof the clock frequency generating means (H1) associated with the firstcounter (21), then there has been carried out a counting operation of aduration greater than a predetermined time T1, without receiving a zeroset signal, T1 being greater than T2.
 10. Electric iron comprising asole plate heated by means of an electric heating resistance (2) and asystem of thermal regulation, in which a control member (4) indicatesthe reference value of temperature corresponding to the cloth to beironed, a detector (5) gives the temperature of the sole plate, and acontrol system (6) controls the opening and closing of the supplycircuit (1) of the electric heating resistance (2), as a function of thedifference between the reference value and the measured value, whereinthe iron further comprises a safety system (10) comprising an electronicmodule (9), which receives from the control system (6) information as toclosure of the supply circuit (1) of the electric heating resistance(2), counts over a fixed time interval the number of alternationsbetween open and closed conditions of the supply circuit (1) of theelectric heating resistance (2), and opens the supply circuit (1) of theelectric heating resistance (2) if the number thus obtained is below apredetermined threshold value.